The present invention relates to a cap for containers which are used to store volatile liquids. The object of the present invention is to provide a cap for containers used to store volatile liquids which can appropriately discharge volatilized gas under ordinary conditions and which can prevent the leakage of liquid when the container is turned upside down or on its side.
The present invention provides a cap for containers, such as gasoline tanks, used to store volatile liquids which is designed so that (a) vaporized gasoline can be effectively discharged so that accidents such as explosions are prevented, and (b) there is no leakage of gasoline when the container is turned over.
The installation of caps on openings in tanks used to store liquids has been a general practice in the past. The caps employed in such cases have been made of metal or a synthetic resin, and are appropriately equipped with packing for sealing purposes.
Furthermore, such caps have been equipped with gas venting ports which incorporate a spring or ball valve; in such cases, gas can be vented under ordinary conditions, and when the tank is turned over, the gas venting port is blocked by the abovementioned spring or ball so that leakage of the volatile liquid is prevented.
In the case of the abovementioned conventional caps, the gasoline inside the tank vaporizes so that the gas pressure is increased when the temperature around the tank rises. This leads to a danger of explosion, and is extremely dangerous even if an explosion does not occur, i.e., the gas may jet out when the cap is removed. Accordingly, the areas where such tanks may be stored are necessarily restricted and, for example, the use of such general caps is not allowed in the case of tanks installed in automobiles.
Caps equipped with a gas venting port which has a blocking means such as a spring or ball make it possible to eliminate the disadvantages of the abovementioned conventional caps. However, such caps are expensive and have a complicated structure. Furthermore, in the case of long-term use, the action of such caps may be hindered by rusting or fouling of the spring so that the desired action cannot always be obtained. Furthermore, such caps also suffer from the disadvantages of increased size.